1. Field of the Invention
The present invention relates to a method for manufacturing a silicon-on-insulator (SOI) substrate. The present invention also relates to a semiconductor device manufactured using the SOI substrate.
2. Description of the Related Art
In recent years, integrated circuits using a silicon-on-insulator (SOI) substrate where a thin single crystal semiconductor layer is present over an insulating surface, instead of using a bulk silicon wafer, have been developed. Because parasitic capacitance between a drain of a transistor and a substrate is reduced by use of an SOI substrate, SOI substrates are attracting attention as substrates which improve performance of semiconductor integrated circuits.
One of known methods for manufacturing SOI substrates is a Smart Cut (registered trademark) method (for example, see Reference 1: Japanese Published Patent Application No. 2000-124092). A summary of a method for manufacturing an SOI substrate by a Smart Cut method is described below. First, by implantation of hydrogen ions into a silicon wafer by an ion implantation method, an ion-implanted layer is formed at a predetermined depth from the surface. Next, the silicon wafer into which hydrogen ions are implanted is bonded to another silicon wafer with a silicon oxide film interposed therebetween. Then, through heat treatment, the ion-implanted layer serves as a cleavage plane and separation into a thin film occurs in the silicon wafer into which hydrogen ions are implanted. Accordingly, a single crystal silicon layer can be formed, over the bonded silicon wafer. The Smart Cut method may also be referred to as an ion implantation separation method.
A method for forming a single crystal silicon layer over a supporting substrate made of glass by using such a Smart Cut method as described above has been proposed (for example, see Reference 2: Japanese Published Patent Application No. 2002-170942). Reference 2 discloses a bonding method in which a silicon nitride film is provided over a surface of one of a single crystal silicon substrate and a supporting substrate in order to prevent impurities in the supporting substrate from diffusing to a single crystal silicon layer side, and a silicon oxide film formed over the silicon nitride film is used as a bonding plane.